FIGS. 1 and 2 respectively illustrate a section of an aircraft fuselage 10 and part of an aircraft central wing box 12.
As FIG. 1 shows, the fuselage 10 comprises numerous structural parts of elongate overall shape. These parts consist for example of longitudinal stiffeners 14 of the fuselage, also referred to as “stringers”, floor crossmembers 16, floor rails 18, and floor support struts 20 also referred to as “posts” connecting the floor crossmembers 16 to circumferential frames 22 of the fuselage. These various parts adopt the overall shape of girders the cross section of which is generally C-shaped, I-shaped, L-shaped, Z-shaped or omega-shaped.
As FIG. 2 shows, the central wing box 12 comprises structural link rods 24 each comprising a tubular central portion 26 and end parts 28 respectively forming attachment yokes.
These various parts were initially made of metal or of carbon.
However, as the use of composite materials is becoming more commonplace in order to reduce the mass of the structure of aircraft, it has become desirable to produce the parts described hereinabove from composite material, at low cost, and in a way that permits high production rates. What is meant by “composite material” is a material based on reinforcing fibers embedded in a matrix acting as a binder, such as a cured resin. The reinforcing fibers may be of metallic or organic nature. In the particular case of structural parts of elongate shape, such as the parts described hereinabove, use is preferably made of carbon fiber because of the very good mechanical properties thereof. The resin is usually a thermosetting resin, for example belonging to the epoxy resin family.
FIG. 3 thus illustrates a stiffener 30 of known type made of composite material, for example from pre-pregs or by infusion with resin. These techniques allow the creation of parts having a cross section that can vary along the part, as illustrated by FIGS. 3A, 3B and 3C which show the stiffener 30 in cross section on planes A-A, B-B and C-C of FIG. 3 respectively. In the case of the creation of parts of constant cross section, these parts can also be produced using pultrusion.
However, certain regions of these parts need to be reinforced. These are generally the regions involved in fixing the parts to other elements of the aircraft structures, such as the regions near the ends of the parts, and sometimes one or more regions in the middle of these parts.
For that reason, metal reinforcing elements 23 are attached to those regions of these parts that are to be reinforced. These reinforcing elements 23 are generally fixed in place by riveting or bolting, making the method of manufacturing these parts complex and costly.
Similarly, FIG. 4 illustrates a structural link rod 24 of known type, made as a single piece in composite material. Given the generally complex shape of the end parts 28 of such a link rod, the manufacture of such a link rod likewise requires a method that is complex and costly.